A percutaneous implant is an object, foreign to the body, that has been placed through the skin to allow a port of entry to inner body spaces and structures. Temporary percutaneous access is required for a wide variety of procedures such as intra-venous fluid administration and hemodialysis. A number of these procedures also require chronic access. Specific examples of applications which benefit from a chronic percutaneous port include hemodialysis access, peritoneal dialysis access, power supply leads and fluid connections for artificial organs, charging for cardiac pacemakers, neuroelectric stimulation of nerves and/or muscles, artificial stimulation and monitoring in various brain implants.
Acute percutaneous access is routinely accomplished with devices constructed of silicone, polypropylene and polyurethane. These devices serve as a mechanism by which to gain blood access, wound drainage and many other applications. The chronic use of such devices, however, commonly results in infection and/or encapsulation of the device by the epidermis. Past attempts to overcome these problems have included a variety of devices constructed of various materials and have included both rigid and flexible devices. These previous attempts, however, have not provided completely satisfactory solutions. For example, rigid implants of various materials with base portions having a plurality of large diameter holes have been tried, the concept being to have tissue grow through the holes to secure the device in place. It is believed that there is inadequate growth of tissue into these devices to provide a completely satisfactory seal to exclude bacteria. The holes of these devices are also spaced so that good tissue ingrowth is unlikely to occur.
The basic design of prior art percutaneous devices includes a rigid central conduit of a biocompatible material attached to a rigid or semi-rigid fenestrated skirt. The conduit need only be large enough to pass the desired cannula size or electrical cable and still have sufficient wall thickness for structural strength. The dimensions of the conduit vary according to the specific application and the skirt thickness can be adjusted to give proper flexibility and tensile strength; the exact values are functions of the physical properties of the particular material used. The diameter of the skirt is normally only large enough to prevent excessive motion of the skin adjacent to the conduit and to distribute stresses over an area of intact skin.
Conduits have been made from a variety of materials including rigid epoxy, rigid polyurethane, polypropylene, polytetrafluoroethylene, carbon, polycarbonate, aluminum and titanium. Skirts have been made from flexible polyurethane, polypropylene, vitreous carbon fabric, dacron or nylon velour, and dacron mesh. Unsuccessful attempts have also been made to use expanded polytetrafluoroethylene (PTFE) as skirt material. These prior attempts specifically found that expanded PTFE having a fibril length of about 30.mu. was unsuitable for skin interfacing due to insufficient interstitial connective tissue formation.
Previous devices have typically suffered from two major disadvantages:
1. Continuing high incidence of infection, due to inadequate sealing around the device. Inadequate sealing of the device into the body allows bacterial ingress and body fluid egress. PA1 2. "Encapsulation" by the epidermis resulting either in isolation or extrusion of the implant from the body.
These phenomena have been a result of the physical properties of the materials used to fabricate the device and the physiological response when the device is placed in vivo.